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Staying Cool: How Heat Affects Multiple Sclerosis

Overheating may make multiple sclerosis symptoms flare. But planning ahead and keeping some cool tools nearby can help you stay comfortable.

The link between multiple sclerosis (MS) and heat has a long history. Before experts had tests to diagnose MS, doctors had a more primitive way of spotting the disease. People suspected of having MS were given the “hot bath test,” in which they got into a tub of hot water to see if it made their symptoms worsen, according to the National Multiple Sclerosis Society.

While that’s not how MS is diagnosed today, understanding the impact that heat can have on your symptoms is still important.

How Heat Affects MS Symptoms

Any rise in body temperature can trigger a spike in MS symptoms. “Heat can cause areas in the nervous system affected by MS to misfire. When this happens, MS symptoms like fatigue can worsen,” says Peter Bergmann, MD, a neurologist with Kaiser Permanente Colorado in Denver. Heat may also cause vision problems — a condition known as Uhthoff’s syndrome, in which vision blurs or dims — according to the Multiple Sclerosis Association of America.

“Any type of heat can cause MS symptoms to act up or worsen,” Dr. Bergmann says. That includes hot and humid weather, a hot shower or bath, overheating during exercise, or an infection that causes fever.

Heat-related symptoms, however, don’t cause permanent damage to the nerves, and the symptoms will subside as soon as the body cools down.

Staying Cool With MS

Bergmann says that heat intolerance shouldn’t keep people with MS from enjoying the outdoors or exercising. "There are ways to help your body stay cool when faced with any type of heat,” he adds.

Try these tips to manage heat intolerance from MS:

Stay indoors when the temperature rises. Try to plan your outdoor activities early or late in the day rather than when the sun is at its peak. Wear lightweight clothing made of breathable fabrics when you’re out on a hot day.

Wear cooling garments. “Wearing cooling garments, such as a cooling vest, a cooling bra, or a cooling scarf, can be helpful to lower body temperature and avoid an increase in fatigue and other MS symptoms,” says Claire Hara-Cleaver, RN, MSN, CNP, a neurological nurse practitioner at the Cleveland Clinic’s Neurological Institute. Put these items on before heading out into the heat instead of relying on them to cool you down after your body is already warming up.

Stay hydrated. Sweating is your body’s natural cooling process. But if you’re short on fluids, you won’t be able to sweat enough to properly cool down. Stay hydrated by carrying a bottle of water with you throughout the day, drinking frequently. “Water is the best for keeping you hydrated and keeping your core temperature at a normal level,” Bergmann says.

Enjoy a cool treat. Chilled juice or frozen treats can keep your body temperature down. But use caution with electrolyte drinks, Hara-Cleaver says, because they’re high in sugar. Avoid caffeinated beverages as well, including tea and coffee. Caffeine increases urination, which can dehydrate you and decrease your body’s ability to sweat.

Dive into a pool. To stay active, you want to do so in a cool place — and a pool can be ideal. “It's not a cure-all, but it could help keep you cool,” Bergmann says. Taking up swimming or other water aerobics can help you stay fit while giving your body relief from the heat.

Crank up the air conditioning. “Keep the air conditioning on or a fan running when it’s hot out,” Bergmann says. You can also draw the shades or spend time in rooms without direct sunlight heating the room.

Skip the saunas and hot showers. It’s a good idea to avoid any steamy situations, from a sauna to a hot shower or bath. While Hara-Cleaver says that they’re not off-limits for people with MS, be aware that the heat may make you feel weak and fatigued. Stick to a lukewarm shower or cool bath to maintain body temperature. If you want a warmer shower, turn on a ventilation fan or open a window to keep the bathroom cooler.